S. Tapia

Software tool for polarimeter design and evaluation and polarimetric data reduction

We are developing an interactive computer program which includes many of the possible options available for the design of a polarimeter, for the analysis of the output signal, and for the computation of the polarization of the source under investigation. The software is being implemented on a microcomputer and is operated interactively. It utilizes pull-down menus, dialog boxes, graphics and mouse-driven point and click techniques to ease user interaction. We have addressed the issue of how to represent the polarimetric model in software by manipulating optical element transformation matrices (Mueller matrices) to produce the resultant polarimeter matrix. To keep the polarimetric model general and to facilitate analytic evaluations of polarimeter designs we represent these matrices in symbolic form in the software. The software tool will have wide ranging applications in areas of engineering, research and education dealing with polarimetry. It can be used as a design tool for polarimeters in laboratories, remote sensing, or both ground- and space-based astronomy. It can also be used as a simulation tool for polarimetric measurements which will be useful for evaluating polarimeter designs or for educational purposes. The software contains a data reduction tool which can be used to evaluate intensity measurements made by a specified polarimeter.

A search for X-Ray luminous late type stars in NIPSS data

The purpose of this project is to obtain optical identifications of x-ray luminous late type stars. Our approach consists of detecting position coincidences between unidentified x-ray sources and stars for which (V-I) > 3 mag., as obtained from the Near Infrared Photographic Sky Survey (NIPSS) database. Objects with effective temperatures below 3000 K are the most frequent counterparts found by this method at high galactic latitudes (Craine 1987). In this paper we present a derivation of the detection limits of the NIPSS relevant to the lower main sequence dwarf stars. Significantly, M8 or M9 stars with apparent V magnitudes below the detection limit may still appear on the NIPSS I band photographs, where the detection limit is extended to pre-main sequence objects of about 0.03 solar luminosity.